Abstract
We apply proper orthogonal decomposition (POD) technique to analyze granular rheology in a laboratory-scale pulsed-fluidized bed. POD allows us to describe the inherent dynamics and energy budget in the dominant spatio-temporal modes in addition to identifying spatial coherence. This enables us to elucidate non-linear interactions between the different mechanisms which has been a shortcoming of conventional statistics-based approaches. The bubbling pattern is a result of interplay between the harmonic and sub-harmonic components. The mesoscopic flow features which contribute to the pattern are dependent on the modal energy budget which change with the pulsing frequency. It is also observed that the granular dynamics can be sufficiently reconstructed by the leading POD modes despite the presence of bubbles which represent kinematic shocks contributing to higher-order modes. In short, we highlight the utility of POD while analyzing fluidized granular flows, and pave the way for future analyses.Graphic abstractRaw tracks of experimental data (4Hz)
Highlights
Fluidization involves modifying the characteristics of particle-phase to behave as a fluid, thereby enhancing mixing and heat transfer properties
We demonstrate the applicability of proper orthogonal decomposition (POD) to understand granular dynamics in a pulsed-fluidized bed system
The paper is structured as follows: first, we outline the experimental setup and the POD approach; second, we derive time-averaged statistics from raw particle-velocity data obtained using particle tracking; third, we apply POD on instantaneous flow-field and explain the features observed in leading POD modes followed by a low-order reconstruction using these modes; we summarize our findings in the conclusions section
Summary
Fluidization involves modifying the characteristics of particle-phase to behave as a fluid, thereby enhancing mixing and heat transfer properties. It is common in several industrial applications including combustion, gasification, catalytic cracking and food processing [29]. Of particular interest is dense-bubbling fluidization, which is the most common mode of operation in large-scale systems. It is difficult to control the homogeneity of properties like temperature and species composition. This is largely due to voids or bubbles which provide paths of least resistance to the gas phase leading to minimal contact with the solid particles. Complex inter-phase and particle interactions result in a highly nonlinear system [14]
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